JPH0132214Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a radio interference removal device in an information reproducing device that reads information recorded on a record carrier as a change in capacitance and converts it into an electrical signal.

[Technical background of the invention]

2. Description of the Related Art A capacitive pickup type video disk player is a device that records information on a record carrier, such as a recording disk, and reproduces the recorded information.

Such a video disk player records an FM-modulated carrier wave signal on a conductive plastic disk as changes in countless irregularities called pits, and the recorded signal is transferred between the metal electrode attached to the stylus and the conductive disk. Regeneration can be performed by detecting the capacitance change between.

The outline of such a reproducing device will be explained with reference to FIGS. 1 and 2. The capacitance ΔC between the disk A on which the signal is recorded and the stylus 1 changes as the degree of modulation of the carrier wave recorded on the disk. It's coming. This capacitance ΔC is connected, for example, to a 910 MHz tuned circuit in a resonator C driven by a 915 MHz oscillator B. When a capacitance change occurs from the stylus, the characteristic a of the resonator C changes within the range shown by the dotted line as shown in Figure 2, modulating the resonant frequency of the 910MHz tuned circuit,
Change the operating point of 915MHz oscillator B that drives resonator C. This means that the oscillation output frequency of oscillator B is the second
As shown by ₀ in the figure, it is set at the slope part of the resonant frequency characteristic a in the resonator C, so when the capacitance change described above occurs, the 915MHz signal is sequentially amplitude modulated.
Signal b is now applied to peak detector D. An FM signal is obtained as the output of this peak detector D, and this corresponds to the FM wave recorded on the disk. The output of the peak detector D is supplied to an FM demodulation circuit, etc. via a preamplifier E, and an automatic frequency control circuit (hereinafter referred to as AFC circuit) F is provided between the preamplifier E and the resonator C. ing.

On the other hand, information is recorded on disk A as shown in FIG.

FIG. 3 is an explanatory diagram showing signals recorded on disk A in an easy-to-understand manner. To explain this diagram,
Pit row T where video signals and audio signals are recorded
Tracking signals _p1 and _p2 of two different frequencies are recorded intermittently (horizontal synchronization signal portion) on both sides of the (information track). Also, this tracking signal is transmitted to the above _p1 and _p2 every time the disk goes around once.
Since the position of the stylus electrode relative to the stylus electrode surface (right or left relative to the tip of the needle) alternates, a switching signal _p8 is recorded in the vertical synchronizing signal portion V as a means for detecting this.

The disk A on which such tracking information is recorded is placed with respect to the stylus 1 as shown in FIG. FIG. 4 is an explanatory diagram illustrating the outline of a servo mechanism for tracking the stylus 1 using the tracking signal, and parts corresponding to those in FIG. 1 are denoted by the same reference numerals.

The stylus 1 is attached to the tip of the stylus arm 2 as shown in FIG.
The lock is always locked by a force applied in the four directions shown in the figure by a servo mechanism, which will be described later. That is, the output terminal 5 of FIG.
The FM signal is applied to input terminal 6 in FIG. This input terminal 6 is connected to a first bandpass filter 7 that takes out _p1 , a second bandpass filter 8 that takes out _p2 , and a third bandpass filter 9 that takes out _p3 .
Of the extracted signals, _p1 and
_p2 is supplied to the switching circuit 10, _p3 is supplied to the detector 11
After detection, it is applied to the synchronous oscillator 12. This synchronous oscillator 12 applies a switching pulse synchronized with the detection pulse of _p3 to the switching circuit 10, switches _p1 and _p2 , and then switches between the first and second detectors 13 and 14 of the next stage.
It is designed to be derived as follows. By doing so, it is possible to prevent a signal in the wrong direction from being supplied to the tracking mechanism of the permanent magnet 15 and the kicker coil 16 provided at the rear end of the stylus arm 2. The signal applied to this mechanism, that is, the kicker coil 16, is obtained by a differential amplifier 17 that differentially amplifies each output of the first and second detectors 13 and 14.
This is a tracking error signal for correcting the position of p1 and p2.As the stylus 1 deviates in one direction, the amplitudes of _p1 and _p2 fluctuate, and the difference is differentially amplified by the differential amplifier 17 to control the servo control. The error signal is applied to the kicker coil 16 from the servo circuit 18 for each tracking timing pulse generated by the synchronous oscillator 12 to perform a tracking action. Therefore, if the detected amplitudes of _p1 and _p2 are equal, the error signal will be zero and the stylus 1 position will not be corrected.

[Problems with background technology]

However, the oscillation frequency of the oscillator B mentioned above is
It falls within the frequency band of radio waves assigned to mobile radio and aviation radio communications, and when a video disc player is used within the radiation area of these communication equipment, the frequency of the oscillator B and the radio waves from the mobile radio equipment will be beat. and the beat signal is FM
There is a risk that it will be mixed into the signal as an interference signal. In other words, the tracking signal _p1 is 511 [KHz] and _p2 is
716 [KHz], _p3 is a signal of 275 [KHz], and if the beat signal is close to these frequencies, it may be detected as a tracking signal, or the tracking signal may be buried by the beat signal and not detected at all. There is a risk of leakage if not done. For this reason, it may be detected as an amplitude fluctuation of _p1 , _p2 , or the position of the stylus 1 may not be corrected even though it is required. If this happens, the stylus 1 will fly off and several frames will not be played back, or in the worst case, playback will become impossible.

Conventionally, in order to avoid beat interference caused by such external radio waves, the best countermeasure under the present circumstances has been to perform extremely strict shielding on the playback device side.

[Purpose of invention]

The present invention has been made in view of the above circumstances, and is an information reproducing apparatus including an oscillator in a means for reading information from a record carrier on which information is recorded, which includes generating a beat with the oscillation frequency of the oscillator.
To provide a radio wave interference removal device for an information reproducing device capable of avoiding adverse effects on the reproducing device due to the interference when foreign radio waves that are mixed into a reproduced signal as an interfering signal enter.

[Summary of the idea]

That is, the present invention takes into account that the tracking signal is recorded in the horizontal and vertical synchronization signal parts of the disk, and normally the read signal is passed through only the period in which the tracking signal is included, and the signal is recorded in the horizontal and vertical synchronization signal parts. If there is a damage prevention signal in the period that does not include the tracking signal, but if the interference signal is included in the period in which the tracking signal is passed,
This device prevents the signal from passing during the period of the disturbance signal by outputting the logical sum of the pulse that detects the disturbance signal and the pulse that allows the tracking signal to pass.

[Example of idea]

The present invention will be described below with reference to the illustrated embodiments.

FIG. 5 is a block diagram showing an embodiment in which the stylus of the present invention is applied to a playback device that picks up signals recorded on an information track while controlling tracking. In this figure, 21
2 is an input terminal for the FM signal derived from the output terminal 5 in FIG. 1, and 22 is an input terminal for the video signal after the FM signal is demodulated by a demodulator (not shown).
Therefore, the signals at the input terminal 21 include the tracking signals _p1 , _p2 and the switching signal _p3 .
Further, the signal at the input terminal 22 includes horizontal and vertical synchronization signals.

The input terminal 21 is connected to each input terminal of an interference signal detection circuit 23 and a switch circuit 24, which are composed of, for example, a peak detector, etc., and the interference signal detection circuit 2
The output terminal of the switch circuit 24 is connected to one input terminal of the logic adder 25, and the output terminal of the switch circuit 24 is connected to the input terminal of a tracking circuit 26 corresponding to the tracking servo circuit shown in FIG. It is connected to the input terminal 6 in FIG.

On the other hand, the input terminal 22 is connected to an input terminal of a gate pulse generation circuit 27. This gate pulse generation circuit 27 is a circuit capable of separating and detecting frequencies with a circuit configuration similar to a synchronization separation circuit in a television receiver, for example. The vertical synchronizing signal read from the source and the horizontal synchronizing signal of the portion where _p1 and _p2 are recorded are extracted and routed to one path. The output terminal of the gate pulse generation circuit 27, which is this derivation path, is connected to the other input terminal of the logic adder 25.
The output terminal of the logic adder 25 is connected to the switching control terminal 28 of the switch circuit 24. When a pulse is applied from the logic adder 25 to the switching control terminal 28, the signal output from the switch circuit 24 can be cut during the pulse period.

The operation of the radio interference removal device of the present invention having the above configuration will be explained with reference to FIG. FIG. 6 shows the FM signal waveform G of the input terminal 21 mixed with the interference signal S, the detection waveform H of the interference signal detection circuit 23, the gate pulse waveform I of the gate pulse generation circuit 27,
3 is a waveform diagram showing a logic output waveform J of a logic adder 25 and a signal waveform K passed through a switch circuit 24. FIG.

Assume that there is an interference signal S in the FA signal of the input terminal 21 as shown in FIG. 6G. This interference signal S is generally larger than the amplitude of the tracking signal, and the period during which this interference signal S and the tracking signal overlap
At T ₁ , if the device of the present invention is not present, it will be directly applied to the input terminal 6 in FIG. The signal frequency component is detected as one of the tracking signals. Therefore, in the present invention, before inputting the FM signal to the tracking circuit 26, the switch circuit 24
, so that only the tracking signal is supplied to the tracking circuit 26. A signal for passing only this tracking signal is obtained by a logic adder 25. Therefore, when there is no interfering signal, the logic output of the logic adder 25 and the gate pulse of the gate pulse generation circuit 27 are the same.

If the interference signal mixes into the tracking signal period as in the T1 period in FIG. _6G , the interference signal is converted into pulses and detected by the interference signal detection circuit 23. The positive pulse in FIG. 6H indicates this detection pulse. When this detection pulse and the gate pulse (negative pulse in the figure) from the gate pulse generation circuit 27 are input to the logic adder 25, the logical sum output has a high level in the shaded part shown in FIG. 6J, and the FM The signal level reaches a point where the signal can be cut.
With this, even if there is a tracking signal during the period _T1 when there is an interference signal during the tracking signal period, it can be cut off. In other words, the logic adder 25 logically adds the detection pulse to the gate pulse of the interference signal period _T1 .

Furthermore, if an interfering signal is mixed into the normal signal period (period T ₂ in Fig. 6), the output waveform J of the logic adder 25 has no level fluctuation due to the detection pulse, so the FM signal is directly cut off. I can do it.

In this way, even if an interfering signal is mixed into the tracking signal period or any other signal period, the signal can be prevented from being derived from the switch circuit 24 during the period when the interfering signal is present, and unnecessary signals can be input to the tracking circuit 26. never be done. Therefore, it is possible to prevent the stylus 1 from flying off due to a tracking malfunction, or from becoming unable to play.

[Effect of idea]

As explained above, according to the present invention, only the tracking signal is selectively derived, and even if an interfering signal is superimposed during this derivation period, the signal is removed during the interfering signal period. This has the effect of reducing tracking malfunctions due to
Furthermore, the circuit configuration is simple, and it is possible to provide a radio wave interference removal device that has no practical difficulties.

The present invention not only eliminates interference caused by external radio waves, but also differs from conventional tracking circuits in that it supplies only tracking signals to the tracking circuit, as is clear from Figure 4. It is one of the

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the outline of an information reproducing device, FIG. 2 is an explanatory diagram explaining the principle of how information is picked up, FIG. 3 is an explanatory diagram explaining information recorded on a disk, and FIG. 5 is an explanatory diagram for explaining the tracking mechanism, FIG. 5 is a block diagram showing an example of the interference removal device of the present invention, and FIG. 6 is an operation waveform diagram for explaining the operation of FIG. 5. 23... Interference signal detection circuit, 24... Switch circuit, 25... Logical adder, 26... Tracking circuit, 27... Gate pulse generation circuit.

Claims (1)

[Claims for Utility Model Registration] Information is read by a pick-up means from a record carrier on which information is recorded, and tracking control of the pick-up means is performed by a tracking signal included in a predetermined period of a reproduced signal after reading. an information reproducing apparatus comprising: a disturbance signal detection means for detecting a disturbance signal mixed into a reproduction signal by an external radio wave; a pulse generation means for generating a pulse for a period approximately equal to a reproduction period of the tracking signal; logic conversion means for obtaining a logical output between the output of the signal detection means and the output of the pulse generation means; switching means for inputting the reproduction signal and selectively outputting the reproduction signal according to the output of the logic conversion means; 1. A radio interference removal device for an information reproducing apparatus, characterized in that tracking control of the pickup means is performed by a tracking signal selectively taken out from the switching means.